300-410 Mock Exam 87 — 25 Questions

Question 1

An engineer configures MPLS on a router with OSPF as the IGP. The OSPF neighbor is stuck in EXSTART state. The engineer verifies that both routers have matching MTU values on the connecting interfaces. What is the most likely cause of this issue?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The OSPF network type is mismatched between the two routers.. In OSPF, a neighbor stuck in EXSTART is often due to MTU mismatch, but if MTU is confirmed matching, the issue may be a mismatch in OSPF network type (e.g., one side broadcast, the other point-to-point). This causes different behavior in the Database Description (DD) packet exchange, leading to the stuck state even with matching MTU.

Answer

The OSPF hello and dead intervals are mismatched.

Answer

The router ID is duplicated on one of the routers.

Answer

The interface is configured with 'ip ospf mtu-ignore' on one side only.

Question 2

Consider the following partial configuration on router R4:

interface GigabitEthernet0/0
 ip address 192.168.2.1 255.255.255.0
 ipv6 address 2001:db8:1::1/64
 ipv6 ospf 1 area 0
!
interface GigabitEthernet0/1
 ip address 10.0.0.1 255.255.255.0
 ipv6 address 2001:db8:2::1/64
 ipv6 ospf 1 area 0
!
ipv6 router ospf 1
 router-id 4.4.4.4

What is the effect of this configuration?

Accepted Answer

OSPFv3 will form adjacencies on both interfaces as intended because the router-id is correctly set and OSPFv3 is enabled on each interface.. OSPFv3 (OSPF for IPv6) uses a 32-bit router-id, which can be an IPv4 address (like 4.4.4.4) or any arbitrary 32-bit value, and does not require an IPv6 address. The configuration enables OSPFv3 process 1 under the global 'ipv6 router ospf 1' command, sets the router-id, and activates OSPFv3 on both interfaces with 'ipv6 ospf 1 area 0', allowing adjacencies to form normally on both GigabitEthernet0/0 and GigabitEthernet0/1.

Answer

OSPFv3 will not form adjacencies because the router-id must be an IPv6 address.

Answer

OSPFv3 will only form adjacency on GigabitEthernet0/0 because the router-id is not configured under the interface.

Answer

OSPFv3 will not form any adjacency because the network type is not specified.

Question 3

An engineer configures EIGRP named mode on two routers in the same AS. One router uses classic mode configuration. The routers fail to form an adjacency. Which is the most likely explanation?

Accepted Answer

Named mode and classic mode are incompatible and cannot form an adjacency under any circumstances.. EIGRP named mode and classic mode use different packet formats and TLVs, making them incompatible at the protocol level. Even though both operate within the same autonomous system, the routers cannot form an adjacency because the hello packets are not recognized by the other mode. This incompatibility is fundamental and cannot be overcome by configuration adjustments.

Answer

The K values must match exactly, but named mode defaults to different K values than classic mode.

Answer

Named mode requires authentication, while classic mode does not.

Answer

The routers must be in the same autonomous system number, but named mode uses a different AS number format.

Question 4

A network engineer runs the following command to troubleshoot an EIGRP issue:

R1# show ip eigrp neighbors detail

IP-EIGRP neighbors for process 100
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                           (sec)         (ms)       Cnt Num
0   10.1.2.2                Gi0/0            13 00:12:34   12   200  0  145
   Version 12.4/1.2, Retrans: 0, Retries: 0, Prefixes: 5
   Topology-ids from peer - 0
   Stub Peer Advertising (CONNECTED STATIC) Routes
   Suppressing queries

What does this output indicate?

Accepted Answer

The neighbor is a stub router that only advertises connected and static routes, and it does not participate in query propagation.. The output shows 'Stub Peer Advertising (CONNECTED STATIC) Routes' and 'Suppressing queries', which indicates the neighbor is configured as an EIGRP stub router. A stub router advertises only connected and static routes (as specified) and does not participate in query propagation, meaning it will not forward queries from other routers, reducing the query domain and improving convergence.

Answer

The neighbor is a normal EIGRP peer that forwards all routes and queries.

Answer

The neighbor is not forming an adjacency due to a version mismatch.

Answer

The neighbor is using a different autonomous system number.

Question 5

Router R8 is configured with SNMP and IP SLA. The IP SLA operation sends SNMP traps to the NMS when a threshold is crossed. The configuration includes: ip sla 1, icmp-echo 192.168.1.1, threshold 100, timeout 1000, frequency 10, ip sla schedule 1 life forever start-time now, snmp-server enable traps ip sla. However, the NMS receives no traps when the threshold is crossed. The IP SLA operation shows 'Over threshold' in show ip sla statistics. What is the root cause?

Accepted Answer

The IP SLA operation is missing the 'ip sla reaction-configuration' command to trigger SNMP traps when the threshold is exceeded.. The 'ip sla reaction-configuration' command is required to define the condition (e.g., threshold violation) that triggers an SNMP trap. Without this command, the IP SLA operation can detect and report 'Over threshold' in statistics, but it has no mechanism to generate an SNMP trap to the NMS. The 'snmp-server enable traps ip sla' command only enables the router to send IP SLA traps globally; it does not link a specific reaction to the threshold event.

Answer

The NMS is not configured to receive IP SLA traps.

Answer

The SNMP community string is incorrect for trap sending.

Answer

The IP SLA operation is not scheduled correctly.

Question 6

Router R1 is configured with ip nat inside source list 100 interface GigabitEthernet0/1 overload. Internal hosts can access the internet, but traffic to a specific external server at 203.0.113.100 is being translated to a different source IP than expected. Router R1 shows: show ip nat translations: Pro Inside global Inside local Outside local Outside global --- 10.1.1.1 192.168.1.1 203.0.113.100 203.0.113.100. The server logs show connections from 10.1.1.1 instead of 203.0.113.1. What is the root cause?

Accepted Answer

The interface GigabitEthernet0/1 has a private IP address; configure a public IP or use a NAT pool.. The NAT configuration uses `ip nat inside source list 100 interface GigabitEthernet0/1 overload`, which translates inside local addresses to the IP address of the GigabitEthernet0/1 interface. If that interface has a private IP address (e.g., 10.1.1.1), then all translated traffic will appear to come from that private address, not a public one. The server logs confirm this by showing connections from 10.1.1.1 instead of a public IP like 203.0.113.1, indicating the interface lacks a public IP or a NAT pool with a routable address.

Answer

The access-list 100 is incorrectly matching traffic.

Answer

The server is responding to the wrong IP due to asymmetric routing.

Answer

The NAT configuration is missing the 'overload' keyword.

Question 7

An engineer configures EIGRP named mode on two routers in an MPLS L3VPN. The routers are directly connected and can ping each other. The engineer notices that the EIGRP adjacency forms but then the neighbor relationship goes down and the routers become stuck-in-active (SIA) for certain routes. The engineer checks the logs and sees no errors. What is the most likely explanation?

Accepted Answer

The 'metric weights' (k-values) are mismatched between the two routers, causing query propagation to fail.. In EIGRP named mode, the default hello interval and hold time are different from classic mode. Named mode uses a default hello interval of 5 seconds and hold time of 15 seconds, while classic mode uses 5 and 15 as well, but the key difference is that named mode uses a different metric calculation (wide metrics) by default. However, the most common edge case causing SIA in named mode is that the 'metric weights' or 'k-values' must match between neighbors. If one router is using named mode with default k-values (1,0,1,0,0) and the other is using classic mode with different k-values (e.g., 1,0,1,0,0), the adjacency will form but queries may not be processed correctly, leading to SIA. Additionally, named mode requires the 'address-family' configuration to be consistent. A more specific edge case is that named mode uses a different 'graceful-restart' mechanism by default, which can cause issues if not supported on both sides.

Answer

The 'auto-summary' command is enabled on one router, causing route summarization to break the adjacency.

Answer

The 'passive-interface' command is applied to the interface, preventing the adjacency from forming.

Answer

The 'bandwidth' setting on the interface is set to a very low value, causing the EIGRP metric to be too high for the route to be installed.

Question 8

An engineer is troubleshooting why the NMS is not receiving SNMP traps for interface up/down events on router R4. The configuration includes 'snmp-server enable traps snmp linkdown linkup' and 'snmp-server host 10.1.1.200 version 2c public'. The NMS can receive other traps from R4. What is the most likely cause?

Accepted Answer

The engineer combined 'linkdown' and 'linkup' in a single command; they must be configured as separate 'snmp-server enable traps' commands.. Cisco IOS requires that 'linkdown' and 'linkup' be configured in separate 'snmp-server enable traps' commands when using the 'snmp-server enable traps snmp' syntax. Combining them in a single command is syntactically invalid; the router will not enable either trap type, which explains why the NMS receives other traps but not link up/down events.

Answer

The NMS is configured to filter out link up/down traps, so they are not displayed.

Answer

The router needs the 'snmp-server trap-source' command to specify the loopback interface for traps.

Answer

The 'snmp-server host' command must include the 'udp-port' option to specify port 162.

Question 9

A network engineer runs the following command to troubleshoot a Route Redistribution issue:

R1# show ip route summary

And sees the following output:

Route Source    Networks    Subnets    Replicates    Overhead    Memory (bytes)
connected       2           0          0             0           512
static          1           0          0             0           256
ospf 1          5           0          0             0           1280
eigrp 100       3           0          0             0           768
bgp 65000       2           0          0             0           512
internal        1           0          0             0           256
Total           14          0          0             0           3584

What does this output indicate?

Accepted Answer

The router has 14 routes total, with OSPF contributing the most routes.. The show ip route summary output provides a count of routes from each source. It shows that OSPF has 5 routes, EIGRP has 3, BGP has 2, and static has 1. This can help identify if redistribution is working by comparing expected routes.

Answer

The router is not redistributing any routes because the counts are low.

Answer

BGP is the only protocol with external routes.

Answer

EIGRP has 3 routes, all of which are redistributed from OSPF.

Question 10

A network engineer runs the following command on Router R1:

R1# show bfd neighbors detail

IPv4 Sessions
NeighborAddr      LD/RD         Int        State         Holdown(mult)  Intf
10.1.1.2          1/3           Gi0/0      Up            3000(3)        Gi0/0

Session state is UP and not using echo function.
OurAddr: 10.1.1.1
Handle: 1
Local Diag: 0, Demand mode: 0, Poll bit: 0
MinTxInt: 1000000, MinRxInt: 1000000, Multiplier: 3
Received MinRxInt: 500000, Received Multiplier: 3
Holddown (hits): 1500(0)
Rx Count: 200, Tx Count: 200

Based on this output, what is the holddown timer value in milliseconds and why?

Accepted Answer

The holddown timer is 3000 ms, but the output shows 1500 ms because the holddown timer displayed is half of the actual holddown time.. The holddown timer is calculated as the maximum of the local MinRxInt and the received MinRxInt, multiplied by the multiplier. Local MinRxInt is 1000000 microseconds, received MinRxInt is 500000 microseconds. The maximum is 1000000 microseconds. Multiplied by 3 gives 3000000 microseconds = 3000 ms. However, the output shows 1500 ms. This is because the holddown timer displayed is actually half of the calculated value due to a Cisco implementation detail where the holddown timer is divided by 2 for display purposes. The actual holddown time is 3000 ms.

Answer

The holddown timer is 1500 ms, which is the received MinRxInt (500 ms) multiplied by the multiplier (3).

Answer

The holddown timer is 1500 ms, which is the local MinRxInt (1000 ms) multiplied by the multiplier (3) divided by 2.

Answer

The holddown timer is 3000 ms, and the output is correct as is.

Question 11

An engineer must configure IP SLA tracking to trigger a static route removal when a remote server becomes unreachable. Which TWO configuration steps are required? (Choose TWO.)

Accepted Answer

Configure 'ip sla 1 icmp-echo 10.1.1.1' and 'ip sla schedule 1 life forever start-time now'.. To track IP SLA reachability, you must first create an IP SLA operation (e.g., type icmp-echo) and schedule it. Then, create a track object that references the IP SLA operation's return code. Finally, apply the track to the static route using the 'track' keyword. The 'reaction' configuration is optional for basic tracking.

Answer

Configure 'ip route 0.0.0.0 0.0.0.0 10.1.1.2 track 1' to apply the tracking to the default route.

Answer

Configure 'ip sla reaction-configuration 1 react reachability' to enable reaction on reachability change.

Answer

Configure 'ip sla logging traps' to enable syslog messages for IP SLA state changes.

Question 12

Drag and drop the steps to configure OSPF inter-area summarization on an ABR into the correct order, from first to last.

Accepted Answer

Enter OSPF router configuration mode. First, enter OSPF configuration mode for the process. Then, configure the area where the routes originate. Next, apply the range command to summarize prefixes into that area. After that, verify the summary route is present in the routing table. Finally, check that the summary is advertised to neighboring areas.

Question 13

An engineer is troubleshooting a DHCPv6 stateful (DHCPv6) deployment. The router is configured as a DHCPv6 server with a pool for prefix 2001:db8:2::/64. Clients on the LAN are configured to use DHCPv6, but they are not receiving IPv6 addresses. The router interface has 'ipv6 address 2001:db8:2::1/64' and 'ipv6 dhcp server DHCP_POOL'. The engineer sees that the clients are sending SOLICIT messages, but the router sends no REPLY. What is the issue?

Accepted Answer

The DHCPv6 pool is missing the 'address prefix 2001:db8:2::/64' command.. For stateful DHCPv6, the router must also send Router Advertisements with the 'M' (Managed) flag set to indicate that clients should use DHCPv6. Without the 'ipv6 nd managed-config-flag' command, clients may not request addresses via DHCPv6, or the server may not respond appropriately. However, the symptom says clients are sending SOLICIT messages, so they are attempting DHCPv6. The router is not replying, which could be due to a misconfigured pool or the server not being enabled. The most likely cause is that the DHCPv6 pool does not have an 'address prefix' statement, so the server has no addresses to assign.

Answer

The interface is missing the 'ipv6 nd managed-config-flag' command.

Answer

The router needs the 'ipv6 dhcp relay' command on the interface.

Answer

The 'ipv6 unicast-routing' command is missing globally.

Question 14

Which TWO statements about IPv6 manual tunnels (IPv6-in-IPv4) are true? (Choose TWO.)

Accepted Answer

The tunnel mode must be configured as tunnel mode ipv6ip.. The `tunnel mode ipv6ip` command explicitly configures the tunnel interface for IPv6-in-IPv4 manual tunneling. This mode encapsulates IPv6 packets directly into IPv4 packets using protocol type 41, as defined in RFC 4213. Without this mode, the tunnel interface would not properly handle the encapsulation and decapsulation of IPv6 traffic over an IPv4 infrastructure.

Answer

Manual tunnels support multicast traffic natively.

Answer

The tunnel destination can be a multicast IPv4 address.

Answer

The IPv4 address of the tunnel source is automatically embedded in the IPv6 prefix.

Question 15

Given this configuration:
```
interface GigabitEthernet0/4
 ip access-group BLOCK_FTP in
!
ip access-list extended BLOCK_FTP
 deny tcp any any eq 21
 deny tcp any any eq 20
 permit ip any any
```
What is the effect of this ACL when applied inbound on GigabitEthernet0/4?

Accepted Answer

It blocks all FTP traffic entering the interface, but permits all other IP traffic.. The ACL is applied inbound on GigabitEthernet0/4, meaning it filters traffic as it enters the interface. The first two deny statements block TCP traffic destined for ports 21 (FTP control) and 20 (FTP data), which are the standard ports for FTP. The final permit ip any any allows all other IP traffic. Thus, only FTP traffic is blocked, and all other IP traffic is permitted.

Answer

It blocks all FTP traffic leaving the interface.

Answer

It permits FTP traffic and blocks all other IP traffic.

Answer

It has no effect because the ACL is missing a sequence number.

Question 16

A network engineer configures SPAN on a Cisco Catalyst switch to monitor traffic between two hosts. The engineer configures the source interface as GigabitEthernet0/1 and the destination interface as GigabitEthernet0/2. After the configuration, the engineer notices that the monitored traffic is not being forwarded to the destination port. What is the most likely cause?

Accepted Answer

The destination port is in a blocking state due to Spanning Tree Protocol.. SPAN destination ports must be configured with the 'spanning-tree portfast' command to avoid being blocked by Spanning Tree Protocol (STP). Without this, the destination port may remain in a blocking state.

Answer

The destination port is not in the same VLAN as the source port.

Answer

The destination port is configured as a trunk port.

Answer

The source interface is not in the same VLAN as the destination interface.

Question 17

Which RFC defines the IPv6 Neighbor Discovery Protocol that is the basis for many First Hop Security features?

Accepted Answer

RFC 4861. RFC 4861 defines the IPv6 Neighbor Discovery Protocol (NDP), which is the foundation for IPv6 First Hop Security (FHS) features. NDP replaces ARP in IPv6 and provides address resolution, router discovery, neighbor unreachability detection, and redirect functions, all of which are leveraged by FHS mechanisms like RA Guard, DHCPv6 Guard, and Source Address Validation Improvement (SAVI).

Answer

RFC 2460

Answer

RFC 4291

Answer

RFC 4443

Question 18

A network engineer configures Flexible NetFlow on a router to monitor traffic on a trunk interface with multiple VLANs. The flow monitor is applied to the physical interface. The engineer notices that all flows show the same VLAN ID in the collector, even though traffic from different VLANs is present. What is the most likely cause?

Accepted Answer

The flow record does not include any VLAN match fields.. To capture VLAN information in Flexible NetFlow, the flow record must include 'match dot1q vlan' or 'match vlan' fields. Without these, the VLAN ID is not recorded, and the collector may show a default or incorrect value.

Answer

The trunk interface is not configured with 'switchport trunk encapsulation dot1q'.

Answer

The flow monitor is applied only to the physical interface, not the subinterfaces.

Answer

The collector does not support VLAN fields.

Question 19

A network engineer runs the following command to troubleshoot a Route Redistribution issue:

R1# show ip bgp vpnv4 vrf CUSTOMER routes

And sees the following output:

Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 100:1 (default for vrf CUSTOMER)
*> 192.168.10.0/24  10.1.1.2                 0    100      0 65001 i
*> 192.168.20.0/24  10.1.1.2                 0    100      0 65001 i

What does this output indicate?

Accepted Answer

The VRF CUSTOMER has two routes learned via BGP from AS 65001.. The show ip bgp vpnv4 vrf output shows routes in a VRF. The routes are learned from neighbor 10.1.1.2 with AS path 65001. This indicates that the VRF is receiving routes via BGP, possibly from a PE router. If redistribution is expected from another protocol into BGP within the VRF, these routes may be the result.

Answer

The routes are redistributed from OSPF into BGP within the VRF.

Answer

The VRF is not receiving any routes because of a redistribution issue.

Answer

The routes are locally originated within the VRF.

Question 20

A network engineer runs the following command on Router R1:

R1# show bfd neighbors detail

IPv4 Sessions
NeighborAddr      LD/RD         Int        State         Holdown(mult)  Intf
10.1.1.2          1/3           Gi0/0      Up            1500(3)        Gi0/0

Session state is UP and not using echo function.
OurAddr: 10.1.1.1
Handle: 1
Local Diag: 0, Demand mode: 0, Poll bit: 0
MinTxInt: 1000000, MinRxInt: 1000000, Multiplier: 3
Received MinRxInt: 1000000, Received Multiplier: 3
Holddown (hits): 1500(0)
Rx Count: 120, Tx Count: 150

Based on this output, which statement is correct?

Accepted Answer

The BFD session is up and the holddown timer is 1500 ms, which is correct based on the configured multiplier and MinRxInt.. The output shows BFD session details. The Holddown value of 1500 ms is calculated as MinRxInt * Multiplier (1000 ms * 3 = 3000 ms), but the output shows 1500 ms. This discrepancy indicates a misconfiguration or a bug, but the key point is that the session is UP and the holddown timer is 1500 ms, which is half of the expected value. However, the correct interpretation is that the BFD session is established and operating, and the holddown timer is 1500 ms as shown.

Answer

The BFD session is down because the holddown timer is incorrect.

Answer

The BFD session is using echo mode, which is why the holddown timer is 1500 ms.

Answer

The BFD session is up but the multiplier is set to 1, causing the holddown timer to be 1500 ms.